The broad goal of the proposed research is to better understand the cerebellar contribution to sensorimotor integration by investigating the neuronal signal processing associated with the velocity storage aspect of compensatory eye movements elicited by natural visual and vestibular stimuli. The focus is on the vestibulocerebellum (the nodulus/ventral uvula and the flocculus). The neurophysiological studies will be conducted using extracellular single unit recording in the awake rabbit. To put the neurophysiological studies into a behavioral context, the three-dimensional aspects of velocity storage will first be determined in the awake rabbit using eye movement recording. Then, the complex and simple spike activity of nodular/ventral uvular Purkinje cells will be determined in relation to the spatial orientation parameters of velocity storage in three dimensions. Purkinje cells will be categorized according to whether their complex spikes are modulated by visual or by vestibular stimuli and by the orientation of the axis of rotation that produces the strongest modulation. The signal content of the simple spike activity of Purkinje cells with visually modulated complex spikes will be compared and contrasted to that of Purkinje cells with vestibularly modulated complex spikes. The hypothesis is that the medial part of the nodulus/ventral uvula is related to control of the pitch and roll axis time constants and the cross-coupling parameters of velocity storage, while the lateral part is related to control of the yaw axis time constant. In addition, the complex and simple spike activity of floccular Purkinje cells will be determined in relation to velocity storage. The signal content of the simple spike activity of floccular Purkinje cells that have visually modulated complex spikes will be compared to that of nodular Purkinje cells that have similar visually modulated complex spikes. The hypothesis is that the simple spike signals on nodular Purkinje cells will relate to the orientation parameters of velocity storage, while those of floccular Purkinje cells will relate to the temporal response of the eye movements.